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The invention relates to the field of systems for deployment, recovery, servicing, and operation of underwater equipment and methods for utilizing such systems. More particularly, the invention relates to devices and methods for deploying, recovering, servicing, and operating an autonomous underwater vehicle.
Vehicles that operate underwater are useful for performing tasks below the sea surface in such fields as deep water salvage, the underwater telecommunications industry, the offshore petroleum industry, offshore mining, and oceanographic research. (See, e.g., U.S. Pat. Nos. 3,099,316 and 4,502,407). One class of underwater vehicle is designated an autonomous underwater vehicle (AUV). AUVs are so named because they can operate without being physically connected to a support platform such as a land-based platform, an offshore platform, or a sea-going vessel.
Commonly used AUVs are essentially unmanned submarines that contain an on-board power supply, propulsion means, and a pre-programmed control system. In a typical operation, after being placed into a body of water from a surface platform, an AUV will carry out a pre-programmed mission, then automatically surface for recovery. A recovery boat is then dispatched to collect the surfaced AUV. The recovery procedure can be performed directly from the recovery boat or with the assistance of a diver. This procedure entails attaching a lift cable to the surfaced AUV so that it can be hauled out of the water using a crane or winch. Once recovered, the AUV is transferred to the surface platform or other servicing site where data obtained from the mission can be down-loaded, the AUV""s batteries recharged, other components serviced, and new mission instructions programmed into the AUV""s control device. The AUV is then redeployed into the body of water so that it can carry out another mission.
In this fashion, AUVs can perform subsurface tasks without requiring either constant attention from a technician or a physical link to a surface support platform. These attributes make AUV operations substantially less expensive than similar operations performed by underwater vehicles requiring a physical linkage to a surface support platform (e.g., remotely operated vehicles).
AUVs, however, suffer practical limitations rendering them less suited than other underwater vehicles for some operations. For example, because AUVs typically derive their power from an on-board power supply of limited capacity (e.g., a battery), tasks requiring a substantial amount of power such as cutting and drilling are not practically performed by AUVs. In addition, the amount of time that an AUV can operate underwater is limited by the capacity of the on-board power supply. Thus, AUVs must surface, be recovered, and be recharged between missions.
This recovery, servicing, and redeployment step reduces the productive operating time of an AUV. Moreover, it creates the additional expense associated with deployment of a recovery boat, diver, etc. In addition, the recovery and redeployment processes increase the likelihood that the AUV will be damaged. For example, AUVs can be damaged during surfacing by colliding with objects on the sea surface such as the surface support vessel. AUVs can also be damaged during the recovery process by colliding with the recovery cable, the side of a surface vessel or boat, or a portion of the crane or winch. In rough seas, recovery is hampered and made more dangerous by vertical heave, the up and down motion of an object produced by waves on the surface of a body of water. Severe vertical heave can render AUV recovery impractical.
Because AUVs are not physically linked to a surface vessel during underwater operations, communication between an AUV and a remotely-located operator (e.g., a technician aboard a surface vessel) is limited. For example, AUVs typically employ a conventional acoustic modem for communicating with a remotely-located operator. Such underwater acoustic communications do not convey data as rapidly or accurately as electrical wires or fiber optics. Transfer of data encoding real time video signals or real time instructions from a remotely-located operator is therefore inefficient. As such, AUVs are often not able to perform unanticipated tasks or jobs requiring a great deal of operator input without first being recovered, reprogrammed, and redeployed.
The present application is directed to a remotely operable underwater apparatus for deploying, recovering, servicing, and operating an AUV. In one aspect, the apparatus of the invention reduces the frequency of necessary AUV recoveries. In another aspect, the apparatus of the invention reduces the risk of damage to an AUV resulting from the recovery process.
The apparatus of the invention includes a linelatch system that is made up of a tether management system connected to a flying latch vehicle by a tether. The linelatch system can be connected to a surface platform by an umbilical on one end and to an AUV on the other end. In addition to providing a mechanical connection, between the AUV and a surface platform , the linelatch system can also carry power and data between the surface platform (i.e., through the umbilical) and the AUV.
The flying latch vehicle is a highly maneuverable, remotely-operable underwater vehicle that has a connector adapted to xe2x80x9clatchxe2x80x9d on to or physically engage a receptor on an AUV. In addition to stabilizing the interaction of the flying latch vehicle and the AUV, the connector-receptor engagement can also be utilized to transfer power and data. In this aspect, the flying latch vehicle is therefore essentially a flying power outlet for recharging the on-board power supply of an AUV, and a flying data modem for transferring information to and from an AUV (e.g., uploading mission results, downloading revised mission instructions, etc).
The tether management system of the linelatch system regulates the quantity of free tether between itself and the flying latch vehicle. It thereby permits the linelatch system to switch between two different configurations: a xe2x80x9cclosed configurationxe2x80x9d in which the tether management system physically abuts the flying latch vehicle; and an xe2x80x9copen configurationxe2x80x9d in which the tether management system and flying latch vehicle are separated by a length of tether. In the open configuration, slack in the tether allows the flying latch vehicle to move independently of the tether management system. Transmission of heave-induced movement between the two components is thereby removed or reduced.
Accordingly, in one aspect, the invention features a method of servicing an automated submersible vehicle (i.e., an AUV) in a body of water by communicating power, data, and/or materials (e.g., fluids and gases) between a vessel and the automated submersible vehicle. This method includes the steps of: deploying a connector (i.e., a linelatch system) connected to the vessel into the body of water; remotely maneuvering the connector to the automated submersible vehicle; connecting the connector to the automated submersible vehicle; communicating power, data, and/or materials between the vessel and the automated submersible vehicle; and detaching the connector from the automated submersible vehicle. In this method, more than about 50% of the power transmitted to the connector can be transmitted to automated submersible vehicle during the communicating step. This method can also further include the step of retrieving the connector.
Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In the case of conflict, the present specification, including definitions will control. In addition, the particular embodiments discussed below are illustrative only and not intended to be limiting.